Design, fabrication and skin-electrode contact analysis of polymer microneedle-based ECG electrodes

Abstract

Microneedle-based ‘dry’ electrodes have immense potential for use in diagnostic procedures such as electrocardiography (ECG) analysis, as they eliminate several of the drawbacks associated with the conventional ‘wet’ electrodes currently used for physiological signal recording. To be commercially successful in such a competitive market, it is essential that dry electrodes are manufacturable in high volumes and at low cost. In addition, the topographical nature of these emerging devices means that electrode performance is likely to be highly dependent on the quality of the skin-electrode contact. This paper presents a low-cost, wafer-level micromoulding technology for the fabrication of polymeric ECG electrodes that use microneedle structures to make a direct electrical contact to the body. The double-sided moulding process can be used to eliminate post-process via creation and wafer dicing steps. In addition, measurement techniques have been developed to characterize the skin-electrode contact force. We perform the first analysis of signal-to-noise ratio dependency on contact force, and show that although microneedle-based electrodes can outperform conventional gel electrodes, the quality of ECG recordings is significantly dependent on temporal and mechanical aspects of the skin-electrode interface.

System Level Framework for Assessing the Accuracy of Neonatal EEG Acquisition

“…The obtained correlation and power-line noise amplitude compare well with previous studies, which presented correlation values of ~0.99 and power-line noise of ~0.5µV for a dry electrode with 2kΩ impedance [19]. Previous works using the MicroTIPs in the space of electrocardiography (ECG) have shown similar impedance recordings [13]. The SNR of the MicroTIPs was estimated on ECG data (±0.4 V).…”

“…Micro Transdermal Interface Platforms (MicroTIPs) bypass the outermost layer of skin, which largely consists of non-conductive skin cells [13]. This is achieved by using micro-machined needle structures that penetrate the Stratum Corneum, thus making direct contact with the conductive layers of the epidermis beneath.…”

Differences in biocompatibility of microneedles from cyclic olefin polymers with human endothelial and epithelial skin cells

“…Silicon microneedle templates, consisting of 100 mm diameter wafers, were produced by the Tyndall National Institute using the potassium hydroxide wet process described previously. 6 These wafers were covered in microneedles measuring 500 μm tall at a pitch of 1.725 mm. As a result of the wet etching process, microneedles were shaped like octagonal pyramids with a sidewall angle of 71 .…”

“…Microneedle‐based transdermal drug delivery is highly attractive due to its needle‐free nature and potential for self‐administration, with corresponding benefits in increased patient compliance, reduced clinical time, elimination of needle‐stick injuries, and sharps waste . Microneedle‐based devices have also shown significant potential in transdermal diagnostics: electrodes may be used to detect biopotential signals such as ECG or EEG without the use of electrolytic gels or skin preparation, functionalised for applications in electrochemical diagnostics, or used to withdraw fluids for biomarker analysis …”

“…[1][2][3][4] Microneedle-based devices have also shown significant potential in transdermal diagnostics 5 : electrodes may be used to detect biopotential signals such as ECG or EEG without the use of electrolytic gels or skin preparation, functionalised for applications in electrochemical diagnostics, or used to withdraw fluids for biomarker analysis. [6][7][8] A microneedle is a short, sharp, spike-like structure, generally less than 1 mm in length, and is often provided in arrays that may number anything up to several hundred per square centimeter and that can penetrate the epidermal layer of the skin. Although microneedles were originally fabricated using techniques borrowed from the semiconductor industry, injection molding has emerged as a viable alternative for their manufacture, especially as technical advances have facilitated the accurate reproduction of the microscale features associated with microneedles.…”